Many problems can be attributed to the Rover SD1 Efi fuel supply system due to flow and pressure issues. Because of the age of these cars (many of them subject to extended periods off the road) the primary cause is liable to be fuel contamination starting with rust in the fuel tank combined with a damaged tank filter allowing crud into the fuel pump and beyond.

If fuel contamination is not a problem or has been routinely prevented or cured the fuel pump and fuel pressure regulator, being very robust items, are less likely to fail as a result. Indeed, many of them are still operating after 25 years of service for maybe 150,000 miles and even more.

Never-the-less, when they do give problems the actual cause is often elusive because either "too high" or "too low" fuel pressure will create a "rich" or "weak" mixture respectively and, with these symptoms, other components in the Efi system tend to come under suspicion first.

For example, common faults associated with the coolant temperature sensor, throttle pot, airflow meter, extra air valve, ECU, wiring and air leaks can all affect mixture control in one way or another.

Consequently the sure way to establish the fuel supply system works correctly is to perform the prescribed tests. It’s not rocket science and needs just a little time and safe operating practice.

In fact, it is a job worth doing on a routine basis even when problems are not suspected.

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In the attached article, reference is made to measuring static fuel pressure but without specifying all the actual conditions, either static or after switch-off.

Reading various workshop manuals related to the standard fuel supply system, none refer to the actual pressure present in the fuel rail after the system is switched off, specifying only the need to depressurise the system.

So diagnostically, what might be expected when measureing fuel pressure in the fuel rail during or after various conditions?

Because the system is a closed loop except when injectors open or the FPR dumps excess pressure to maintain the design injector differential of 36 psi:

When the pressure is measured:

# by operating the AFM flap with engine not running the pressure will be 36 psi.

# after the engine is swtched off with throttle wide open the pressure will be 36 psi.

# after the engine is swtched off with throttle closed the pressure will be 26 psi.

because the FPR detects nil or very low vacuum at W.O.T. and engine not running AND high vacuum at idle.

So the measured fuel pressure after switch off may be anywhere between 26 and 36 psi depending upon the state of the throttle at the instant the pump stops running and the injectors stop opening.